How to debug JWS/JNLP The easiest way found, that works since 1.5:
set JAVAWS_TRACE_NATIVE=1 set JAVAWS_VM_ARGS=-Xdebug -Xnoagent -Djava.compiler=NONE -Xrunjdwp:transport=dt_socket, address=8989,server=y,suspend=n javaws http://server:port/descriptor.jnlphttp://icoloma.blogspot.com/2005/06/how-to-debug-jwsjnlp.html And somebody report problem of using it, not sure if sun respond to any of those - http://www.dynamicobjects.com/d2r/archives/002859.html